Ments



2 Sheets-Sheet 1.

(No Model.)

J. J. OGONNELL. APPARATUS FOR TELEPHONE EXGHANGES.

Patented Aug 13,1895.

(No Model.) 2 Sheets-Sheet 2.

, J. J. OUONNELL.

APPARATU$ FOR TELEPHONE EXCHANGES.

Patented Aug. 13, 1895.

UNITED STATES P TENT OFFICE.

JOSEPH J. OCONNELL, OF onrcA'co, ILLINOIS, ASSIGNOR, BY MESNE ASSIGN-MENTS, TO THE AMERICAN MASSACHUSETTS.

BELL TELEPHONE COMPANY, OF BOSTON,

APPARATUS FOR TELEPHONE-EXCHANGES.

SPECIFICATION forming part of Letters Patent No. 544,546, dated August13, 1895.

7 A plication filed April 1'7, 1893. Serial No. 470,598- (No model.)

To all whom it may concern.-

Be it known that L'JOSEPH J. OCONNELL, acitizen of the United States,residing at Chicago, county of Cook, State of- Illinois,

have invented certain new and useful Improvements in Apparatus forTelephone-Exchanges, of which [do declare the following to be a full,clear, and exact description, reference being had to the accompanyingdrawro ings, forming part of this specification.

In an application filed by me in the United States Patent Office on the1 7th day of April, A. D.-1893, Serial No. 470,597, there is describedand claimed signal apparatus for [5 telephone'exchanges comprising aseries of visible signals whereby the telephone-operator may determineat a, glance-when any desired line is busy without the necessity ofmaking the usual test of the various lines to ascertain such fact, andin such application also there is described and claimed a series ofvisible signals whereby the operator at the calling office may beinformedwhen the operator at the distant office has made the con- 2nection called for. So also in the above-mentioned application there isdescribed and claimed a visible disconnect signal adapted to becontrolled by passage of current over,

the line-wire, said current passing from a 0 source arranged normallyout of the circuit of the trunk-line. Ido not wish, therefore, to beunderstood as claiming in this specification either of theabove-mentioned features of the invention, although they are shown inthe ac- 5 companying drawings and described in thefollowingspecification.

In my above-mentioned application the current whereby the signals werecontrolled passed between the calling and receiving ofo fices over thetrunk-line. In some cases it is desirable that the trunk-line should notbe used for the signal-current, and one of the features of my presentinvention consists of a supplemental signal-wire extending be- 5 tweenthe exchanges and connected and arranged as hereinafter defined, andover which the signal-current will be passed. A further feature of myinvention consists in connecting to the trunk-line wire and to theseparate signal-wire a special style of spring-jack in the section ofthe multiple board at which the subscribers calls are answered, wherebyI am enabled to employ in. the remaining sections the ordinary twolinespring-jacks of the multiple switchboard.

A further feature of this invention is the employment of relays ofdifiering' resistances for controlling the signal-circuits, ashereinafter defined.

The invention also consists in providing at the receiving office atrunk-line signal (hereinafter termed the sentinel signal) whereby theoperator at such office will be informed that the operator at thecalling office has been notified that the desired connection between thesubscribers telephones has been made. Y

My present invention consists also in various other improvementsrelating to the tea 7o tures above named, all of which are hereinafterdescribed, illustrated in the accompanying drawings, and particularlypointed out in the claims at the end of this specification.-

- Figure l is a diagrammatic view of a telephone-exchange systemembodying my invention, the parts and connections being shown inposition assumed when the various lines are idle or in their normalposition. Fig. 2 is a similar view showingthe parts and connections inposition assumed-when two subscribers telephones are connected by meansof a trunk-line.

The calling office is shown as provided with a subscribers multipleswitchboard A, with the various sections of which a single subscribersline B is shown as connected, this line B consisting of two wires 2 and3 to form a metallic circuit for the subscribers telephone'B'. Theseveral sections a, a, a and go a of they switchboard A are of usualconstruction, the'wires 2 and 3 of the subscribers line B beingconnected, respectively, to the contact-screws 4 and the spring-jackrings 50f these sections. That section, however, 5 of the multipleswitchboard at which all the calls of the subscribers telephoneB areanswered will be' preferably providedwith spring-jacks C of theconstruction shown.

It will be readily understood that when the too operator having chargeof the section of the multiple board comprising the spring-jacks C doesnothing but answer subscribers"calls, the remaining sections a, a, a and0. of the multiple board may be located at a distance more or lessremote. Each of these answeringspringjacks (the one for telephone 13only being shown) comprises a contact-plate c, which by means of thewire 2, and by means of the springs and contact-screws of theswitchboard sections a ct a a are connected with the wire 2, andcomprises also a casing ring 6, which by means of a wire 3 and by meansof the casing-rings 5 of the sections a, a, a and a willconnect with thewire 3 of the subscribers line B. The wire 3 will connect also by abranch wire 3 with a calling drop or annunciator, a return-wire 7leading from the releasing-coil D of the annunciator to the contactspring or plate a of'the jack 0. This jack is furnished also with theplate 0, that is grounded by the wire 9, and with the plate 0 whichconnects by means of a wire 10 with the restoring-coil D of the callingdropor annunciator, this coil D being connected by a wire 11 with thebattery 12, from which a wire 13 leads to ground. The calling drop orannunciator is of the type commonly known as a self-restoring drop, thisdrop having a retaining-hook d for the shutter d, this hook beingpivoted, as at 61 and having its rear end arranged as an armature thatwill be shifted by the releasing-coll D of the drop. The coil D willserve to return the shutter 61 into engagement with the hook d, inmanner well understood in the art.

Assuming that the spring-jack is in its normal position, as shown inFig. 1, at which time no plug'will be therein, it will be seenthatif thesubscriber at the telephone B rings current will pass from the generatorof the telephone B over wire 2, and through the several spring-jacks ofthe switchboard A, and by the wire 2 and its branch 2 to thereleasingcoil D of the calling-drop, thereby attracting the armature dand causing the hook d to release the shutter d. From the releasing-coilD current will pass by wires 3" and 3 through the rings of theswitchboard-sections to the wire 3, and by such wire to the telephone B.The operator at the calling office having charge of theswitchboard-section at which the calls of the telephone B are answeredwill then insert the plug E into the spring-jack O, and will at the sametime retract the plunger 15 of the listening-key F to the position shownin Fig. 2. \Vhen the plug E is thus inserted in the jack 0, it will beseen that current from battery 12 can pass by wire 11 throughwestoring-coil D of the calling-drop, thence by wire to the plate 0 ofthe jack (3, thence by contact-ring e of the plug E to the contactplate0, and thence by wire 9 to ground,thus energizing the coil D and causingit to retract the shutter d into engagement with the hook d of thecalling-drop. It will also be seen that when the plug E is in the jack0,

and the plunger :of the listening-key F is in the retracted positionshown in Fig. 2, the calling operator, by means of her transmitter 18and head telephone 19, can communicate with the subscriber at thetelephone B, the circuits at such time being as follows, viz: From thetelephone B by wire 2 to the contact-screw 4t and springs 4 of theswitchboard A; thence by wire 2 to the contact-plate c and tip 6 of theplug E, from which tip current passes by the wire 20 to the projectingarm 21 that connects to a contact-plate 22 of the ringing-key G; thenceby contact-point23 and plate 24 to wire 25 and branch wire 25 to the arm26 of the contact-plate 27 of the listening-key F; thence by thecontact-point 28 of plate 29 to the wire 30 that leads to the headtelephone 19, from which current passes by wire 31 to the plate 32 andcontact-point 33 to the contact-plate 3a; thence by the arm 34 and wires35 and 36 to the contact-plate 37 and contact-point 38 of theringing-key G; thence by contact-plate 39 and its arm 40 and the wire 41to the sleeve e of the plug E; thence by casing-ring 6 and wire 3 to therings 5 of the switchboard A, and, tinally,by the wire 3 back to thetelephone 13. It will thus be seen that the operator at thecallingoflice will be in communication with the tele phone B to receivethe order. 7

The calling office is shown as provided with a listening key F, theringing-key G, and the ringing-key H,and as well, also, with the keys Kand L. The ringing-key F comprises an insulating-sleeve f, through whichpasses in manner free to slide theshank of the plunger 15, the head ofthis plunger being formed of non-conducting material. Upon one side ofthe sleevef is mounted the contact-plates 3t and 4t, and upon theopposite side of the sleeve fare mounted the contact-plates 27 and 45,these plates being suitably insulated from each other. From one side ofthe sleeve f projects a contact-point 46 that extends through a slotformed in the plate 27 to avoid contact therewith, the outer end of thiscontact-point 46 extending into position to touch at proper time thecontact-plate 45.

The ringing-key G, whereby the operator at the calling office can ringthe bell of the sub scribers telephone 13, comprises a sleeve g ofinsulating material, upon one side of which are mounted thecontact-plates 39 and 47, and upon the opposite side of which sleeve aremounted the contact-plates 22 and 48, the plates being suitablyinsulated, as shown.

The ringing-key H, whereby the operator at the calling oflice can ringthe bell of the distant subscribers connected with the receiving oiiice,comprises a sleeve h of insulating material, at one side of which aremounted the contact-plates 50 and 51, and upon the opposite side ofwhich are mounted the plates 52 and 53, these plates being suitablyinsulated, as shown. The ringing-key G has a plunger g, held in .mannerfree to slide through the sleeve g and furnished with the subscriber atthe telephone B she can do so.

manner the ringing-key H has a plunger h,

arranged to slide within the sleeve h, and provided with a head 72 ofinsulating material.

It will be readily seen that if the operator at the calling officedesires to ring up the by merely depressing the plunger g of the key G,thereby causing the plunger head 9 to force outward the contact-plates39 and 22 until these plates contact, respectively, with thecontact-plates 47 and 48.

erator M, by wire and its branch 56, to the extension of thecontact-plate 48; thence to the contact-plate 22, and by this plate andits extension 21, by wire 20, to the tip of the plug E, whence it willpass by the connection shown to the telephone B and back from suchtelephone, through theconnection shown, to the ring 6 of the spring-jackC; thence to sleeve 6 of the plug E; thence by wire 41 to the extension40 of the contact-plate 39; thence by contact-plate 47 and its extensionto -wire58 that leads to the generator M.

When the operator of the calling office has ascertained from thesubscriber at the telephone Bt the number of the desired subscriber, shewill force in the order-wire key K in order to throw her head telephonein circuit with that of the operator at the distant exchange. Theforcing inward of the keyK will cause the plate is to contact'the withter I minal of the wire 60, will cause the plate 70 to contact with theterminal of the wire 61, and

it will be seen that acircjuit will then be estab-: lished between thetwo operators telephones as follows, viz: from head telephone 19, by

Wire 31 and its branch 31 to the contact plate Z of the key L; thence bywire 60 to the contact-plates 70, by order-wire 62 of the order-line 0through the induction-coil 63, back by wire 64 of the order-line O tothe plate is Y of the key K; thence by wire 61 to the conpass to therelay 71 and thence by wire 72 to' tact-plate Z of the key L, to theterminal of wire 66, to the head telephone 19. By the induction-coil 63current will be established in line spring-jack S in order to establishcommunication between the subscribers springjack 0 and the trunk-lineS', which trunk-line consists of two wires 5 and s to form a metalliccircuit. Byinserting the plug R in the jackS the busy-signal lampT (orother visible signal) will be brought into action in order to indicateto the operator at the calling office thatthe trunk-line S thus pluggedinto is engaged, this lighting of the busy-signal lamp T being effectedin the following manner,'viz: From the battery current will thecontact-plate s of the jack S, by ring 7' of the plug R to thecontact-plate s of the jack;

thence by wire 7.3 to the relay 74 and by wire v By this means currentwill be caused to pass from the genagainst the force of the spring 77.When.

this armature touches the contact-tern1inal78 and thus closes thenormally-open circuit in which is interposed the signal-lamp '1, currentwill pass from the battery 79 to wire 80 through armature 76 andcontact-terminal 78, to wire 81, back to battery 79, and

the signal-lamp T will thus show that the trunk-line S is busy.

The receiving operator having been notified by the calling operator tomake the desired connection, will insert the trunk-line plug S in thespring-jack of the desired subscriber and then retract the key U to theposition shown in Fig. 2, this key being normally in the position shownin Fig. 1, but remaining in the retracting position shown in Fig. 2 solong as the trunk-line S is busy. The retraction of the key U to theposition shown in Fig. 2 will serve, in manner to be next described, toestablish the local circuit, (at the calling office,) in which isinterposed the signal-lamp 20, whereby the operator at the callingoffice will be notified that the operator at the receiving office hasmade the required connection, this signal-lamp being termed, forobnvenience, the O. K.signal. Upon one side of the key U are arrangedthe contact-plates 80, 81 and 82, and upon the opposite side of this keyare arranged the contact-plates 83, 84, and 85, these several platesbeing insulated from each other, as well understood. The plates 80, 82,83, and 85 have their outer ends bent as shown, to be engaged by theenlarged portions of the key U, and the outer end of the plate 84 isengaged by the non-conducting tip 86 that is fastened to the plate 85,and whereby the free ends of the plates 83 and 85 are caused to moveinunison. When the receiving operator has retracted the key U to theposition shownin Fig. 2 and with the several plates of the key in theposition shown in'such figure, it will be seen that the followingcircuit will be established between the subscribers telephones, (itbeing assumed that the operator at the calling office still has thelistening-key F in the subscribers circuit), viz: From the subscriberstelephone B current will pass by wire2 through the multiple board A tothe contact-plates c of spring-jack O; thence to tip e of plug E, bywire 20 to contact-plate 22, by contact-point 23 and extension 24 towire 25, to the extension of the contact 71. to plate 52, and by theextension 52 of this plate to the wire 88, to tip r. of the plug R;thence by the spring 8 of the springjack S to the trunk-line wire 8;thence to the contact-plate 81 of the key U, to contact-plate 82, towire '89, [0 the tip 5 of. the trunk-line plug S thence by means of thesubscribers spring-jack and the subscribers wires to and from thedistant subscribers telephone. The return-current from the distantsubscribers telephone will pass from the ring of the spring-jack to thesleeve 5 of the trunk-line plug S thence by trunk-line wire to the ring91 of the trunk-line spring-jack S; thence by the sleeve 0 of the plug Rto the wire 92; thence by the extension 50 and the plate 50 to thecontact 93; thence by the wire 94: to the plate 37 and contact 38;thence by plate 39 and extension 40 to the wire 41; thence to the sleeve6 of the plug E, and thence by wire 3 to the rings 5 of the multipleswitchboard A, and finally by wire 3 to the subscribers telephone B. Itwill be seen that at the same time that the key U is retracted by thereceiving operator to the position shown in Fig. 2 a circuit will beestablished through the relay 71 in order to close the local circuit ofthe O.K. signal-lamp W, and through the relay 95 in order to close thelocal circuit of the signal-lamp X.

The purpose of the signal'lamp X, which for convenience is termed thesentinel signal, is to notify the receiving operator that the callingoperator has received the O. K. signal and has thus been informed thatthe desired connection has been made. The relays 71 and 95 will now beenergized by passage of current in the following manner, viz: Fromrelay-battery 7 0 current passes through the relay 71, therebyenergizing this relay and attracting its armature 71* against thecontact-point w of the O. K. signal-circuit wire to, which leads tobattery 79, this battery being connected, as shown, with the armature71. Consequently, when the armature 71 is caused to contact with thepoint to, the local signal-circuit of the lamp W will be completed andthis lamp will be caused to burn, thereby indicating to the operator atthe calling office that the required connection of the trunk-line plugwith the distant subscribers spring-jack has been made. It will also beseen that current from battery 70, after passing through relay 71, willpass by wire 72 to contact-plate s of the jack S, by ring 1' of the plugR to the contact-plate s, by signal-wire to the contact-plate 84C of thekey U; thence by terminal-contact 101 to the wire 102; thence to relay95, and by wire 103 to ground. As current thus passes through the relay95, it will energize such relay, thereby attracting its armature 95against the force of the spring 95", causing the armature to bearagainst the contact 104: of the sentinel-signal wire 0:, thus completingthe local circuit (which is normally open) through this signal-wire as,its battery as, and sentinel-signal lamp X, thereby causing the lamp Xto burn and so indicate to the operator at the receiving office that theoperator at the calling office has received notice that the desiredconnection has been made. The coil of the relay 95 is of low resistance,(say fifty ohms,) so that the current from the relay-battery70 as itpasses to the signal-wire S will not escape through the wire 73 to therelay 7t to ground, because, as has been stated, this re lay 74 is ofsuch high resistance (say one thousand ohms) as to check the flow of thecurrent and permit it to pass through the signal wire S to the relay 95in manner above defined. After the calling operator has been notified bythe O. K..signal that the desired connection at the receiving office hasbeen made, she will next force outward the listening-key F and thusthrow the head telephone 19 out of circuit and also move outward theringing-key H to ring up the distant subscriber called for. When theoperator forces outward the ringing-key H, current will pass as follows,viz: from the generator M by wire 55, contact-plates 52 and 53, arm

52 of the plate 52, wire 88, tip 1" of the plug R,

spring-plate s of spring-jack S, trunk-line wire 8', contact-plates 81and 82, respectively, of the key U, wire 89 to the tip 3 of thetrunk-line plug S and from tip 3 to the distant subscribers telephone,as well understood. The return current will pass from the distantsubscribers telephone to the sleeve 8 of the trunk-line plug 3 as wellunderstood. Continuing, the return current will pass from the sleeve 3of the trunk-line plug S by wire 90, trunk-line wire 3, ring 91 of thetrunk-line jack S, sleeve r of the answering-jack R, wire 92, arm 50,and plate 50 of the key H, plate 51 and its extension, wire 58, back togenerator M. The line is now complete between the two subscribers, theoperators telephone is out of the subscribers circuit, and thebusysignal lamps T at the calling office and the sentinel-lamps X at thereceiving office are burning, thus indicating to the operator at thecalling office that the trunk-line O is busy and to the operator at thereceiving office that the operator at the calling office has been dulynotified that the desired connection has been made.

When either of the subscribers rings off, the clearing-out drop Y willbe caused to drop, thus showing to the operator at the calling officethat a disconnection of the subscribers style known as aself-restoring-drop, being similar in construction to the calling-drop Dbefore described. From the releasingcoil y current will pass by wire 111to the contact 71 of the key 11, and thence to contact-plate 52 and bywire 88 to the tip of the plug R, whence it will pass, in mannerhereinbefore described,

to and over trunk-line S to the distant subsoribers telephone, returningfrom which the current will pass to the sleeve 1' of the plug R, to wire92, to plate of key H, to contact 93, and by wire 110 to thereleasing-coil y of the clearing-out drop. When generator-cum,

rent developed by the ringing of the generator at the subscriberstelephone is passed through the clearing-out drop by the circuits lastdefined, the releasing-coil yet this drop will be energized, thusattracting the armature y, so as to raise the hook 1f andrelease thepivoted indicator-shutter y of thedrop,

in order to show to the operator at the calling office that adisconnection of the subscribers telephone is to be made. The operatorat the calling officewillnext remove the plug R from the trunk-line'jackS, thereby disconnecting the subscribers, and this removal of the plug Rwill cause the O. K. signallamps W and the busy-signal lamps T at thecalling office andthe sentinel-lamps X at the receivingoftice to beextinguished, and will also cause thedisconnect-signal lamps Z to burnat the receiving office, in order to indicate to the operator at suchoffice that a disconnection of the subscribers has been made. When theplug R is thus withdrawn from the trunk-line jack S, the passage ofcurrent from battery 70, through relay 71, wire 72, and plate 5 of thejack S is broken, and consequently the armature 71 is retracted by itsspring from the contact 10, and the local circuit through the O. K.signal lamps W is broken. It will also be seen that as current cannotpass from battery'70 be yond the plate 8 of the jack S, the relay 74will be de-energized and its armature 7 6 will be retracted by itsspring away from the contact 78, thereby breaking the local circuitthrough the busy-signal lamp T. So, also, the breaking of currentv frombattery 70, as

. last described, will prevent passage of current from such batterythrough the relay 95 in manner hereinbefore, described, and the relay 95will be de-energized, thereby allowing its armature95 to be withdrawnfrom the contact 104 in order to break the local circuit through thesentinel signal lamp -X. The local circuits of the-several lamps T, W,and

- X being thus broken, these lamps will be extinguished. When thearmature 95 of the relay 95 is retracted by its spring 95*, it will bebrought to bear against the contact-point 112 of the wire 113, therebyclosing at such point the circuit for the passage of current .frombattery to through the disconnect-signal lamp Z; and inasmuch as the keyU will be in the retracted position shown in Fig. 2 at the time thedisconnect-signal is to be given,.the terminal 1140f the wire 113 willbe in contact with the plate 83 of the key U. Consequently current maypass at such time from battery 00 through the disconnect-signal lamp Zby wire 2 to contact-plate 83, to terminal 114, to wire 113, to armature95,

and by wire m to batteryac'. The disconnectsignal lamp will thus becaused to burn and indicate to the operator at the receiving oifice torat the calling office removes the plug R from thetrunk-line jack S, shewill withdraw the plunger 15 of the listening-key F ;in order to throwher head telephone into the trunk-line circuit, and by this inwardmovement of the plunger 15 ot the listening-key F a passage isestablished for current from battery 125" through the restoring-coils L1of the clearing-out drop Y, thence by wire 126 to the extension ofcontact plate 45, thence by contactpoint 46 and wire 12? to ground. Thepassage of current through the restoringcoils 3 will cause the shutter gto be returned into engagement with the hook of the clearing-out drop.Having thus described the invention, what I claim as new, and desire tosecure by Letters Patent, is

1. In a telephone exchange system, the combination with a trunk lineconnecting two offices, of a spring jack wherein said trunk lineterminates at one of said oftices, a supplemen: tal signal wireextending between the .oflices and connected to said spring jack butn0rmally broken at such point, a battery from which current may becaused to pass over said signal wire, said battery being normallydisconnected therefrom, an operators key at the other office to whichsaid signal wire leads, said signal wire being broken adjacent said keyand being adapted-t0 be closed at such point by said key for passage ofcurrent, whereby the passage ofcurrent between the offices over saidsignal wire is notelfected until the trunk line terminal at one officeis inserted in said spring jack, and the operators keyat theother ofticeis shifted.

. 2. In a telephone exchange system, the combination of a trunk lineconnecting two oflices, a spring jack wherein said trunk. lineterminates, a separate signal wire extending between the offices andconnected to said springjack, and a signal operating battery alsoconnected to said spring-jack, a relay interposed between. said signaloperating battery and said spring-jack, and a local signal circuitcontrolled by said relay, whereby when the trunk line is closed at saidspring-jack current will pass from said battery through said relay toclose said local signal circuit.

3. In a telephone exchange system, the combination with a trunk lineconnecting two offices and with aseparate signal wireconnecting saidofiices, of a spring jack wherein said .trunk line terminates and towhich said signal wire connects, said spring jack comprising a sleeve towhich one of the trunk line wires is united, a contact plate to whichthe other of said trunk line wires is united and comprising alsoseparate contact plates or terminals to which the signal wire isconnected and by which said wire is normally broken at said spring jack,substantially as described.

4. In a signaling apparatus for telephone systems, the combination oftwo signals ar ranged in local circuits, two electromagnets of differingresistances for controlling said signal circuits, a source of currentarranged to energize both of said magnets and two outlets for currentleading from the circuits in which said magnets are placed, whereby whencurrent is caused to flow through one of said outlets, one of saidmagnets will be energized and when current is passed through the otherof said outlets, the other of said magnets will be energized.

5. In a signaling apparatus for telephone systems, the combination witha trunk line connecting two exchanges and with a terminal of said trunkline of two signals arranged in circuits, two electro-magnets ofdifiering resistances for controlling said signals, said magnets beingconnected to said trunk line terminal, a source of current arranged toenergize both of said magnets and two outlets for current leading fromthe circuits in which said magnets are placed, whereby when current iscaused to flow through one of said outlets one of said magnets will beenergized and when current is passed through the other of said outlets,the other of said magnets will be energized.

6. In a signaling apparatus for telephone systems, the combination oftwo signals, two electro-magnets of differing resistances forcontrolling saids signals, a source of current arranged to energize bothof said magnets, two outlets for current, a third signal and a magnetfor controlling said third signal, said magnet being placed in one ofthe outlets leading from the source of current by which the magnets areenergized.

7. In a telephone exchange system, the combination with two officesprovided with suitable switchboards and a trunk line connecting saidoffices and having a suitable switch terminal at each of said ofliceswhereby tele phonic communication may be established, of a signalcontrolling circuit extending between the offices, two signals, onelocated at each of said offices, a source of current for said signalcontrolling circuit, said signal controlling circuit being broken atboth of said offices, a trunk line terminal at one of said offices towhich terminal said signal controlling circuit leads and at which it isnormally broken, said terminal being provided with means whereby whenthe desired connection is made thereat with the trunk line said signalcontrolling circuit will be thereby closed at such point, and circuitclosing mechanism at the other office adapted to there complete saidsignal controlling circuit; whereby said signal controlling circuit willremain open until the operator at one office has closed the trunk linecircuit and the signal controlling circuit at said office and until theoperator at the other oiiice has also completed said signal controllingcircuit, the completion of the signal controlling circuit at the lastnamed office serving to bring both signals into operation.

8. In a telephone exchange system, the combination with two offices andaline connecting said offices, said line being provided with suitableterminals whereby telephonic connections may be made, of a signal at oneof said offices whereby the operator at said office can be notified thatthe operator at the other office has made a required connection, asignal at said other office whereby the operator at said office can benotified that the signal at the office first mentioned has been causedto operate; and a signal controlling circuit extending between saidoffices and provided at each office with a relay interposed in saidcircuit for controlling the signal at the corresponding oiiice, saidsignal controlling circuit being normally broken at one of said officesand means at the other of said offices whereby the operator can closesaid signal controlling circuit and thereby permit passage of currentover said circuit to energize the relays and cause both signals toindicate.

9. In atelephone exchange system, the combination with a calling ofiiceand a receiving office, of a conversation line extending between saidoffices, said line being provided with a spring jack at one oifice and aswitch plug at the other office, whereby telephonic communication can beestablished, of a signal at said calling office to indicate to theoperator there that the operator at the receiving oftice has made arequired connection; a sig nal at the receiving oliice to indicate tothe receiving operator that the signal at the calling office has beencaused to indicate, a signal controlling circuit provided at each officewith means for controlling the signal at such point, said signalcontrolling circuit being connected with the conversation line terminalat the calling office and normally open at such point, and beingnormally open at the receiv ing office, and means at said receivingoi'lice for closing said signal controlling circuit at such pointwhereby when the calling operator has closed the signal controllingcircuit at the calling office by the insertion of a plug, the operatorat the receiving office having made the required connection can closethe signal controlling circuit at such point and thereby cause passageof current over said signal controlling circuit in order to bring saidsignals into operation.

10. In a telephone exchange system, the combination with two oflices anda trunk line connecting the same and having a suitable switch-terminalat each of said oiiices, of two signals, one signal being located ateach of said offices, a relay at each of said offices for controllingthe signal atsaid office, suitable circuit connections between saidrelays and IIO the switch-terminal at one office, said terminal being soconnected with the circuit in switch-terminal at each of said offices,of two signals, one signal being arranged in a local circuit at each ofsaid oifices, a relay at each of said offices for controlling the localsignal circuit at said office, suitable circuit connections between saidrelays and the switch-terirninal at one office, said terminal being soconnected with the circuit in which the relays are interposed, that whena trunk line connection is made at such office, both of said signalswill be brought into action, and a source of current for causing theoperation of the relays.

JOSEPH J. OCONNELL.

Witnesses:

JAMES H. PEIROE, FRED GERLAOH.

